Computer-aided drug design of photoactivated platinum anticancer complexes

Platinum(IV) complexes are usually inert and stable compounds which can be photoactive pro-drugs to produce Pt(II) species with promising anti-cancer activity. Studies of the photochemistry of Pt(IV) complexes by time-dependent density functional theory (TDDFT) and spectroscopic methods show close agreement. Broad exploration of cis/trans geometries, trans influences, the nature of the OR− and (pseudo)halogen ligands, electron-withdrawing/donating/ delocalizing substituents on the N-ligands, and intramolecular H-bonds shows that (1) the design of platinum(IV) complexes with intense bands shifted towards longer wavelengths (~330 nm) can be achieved by introducing intramolecular Hbonds involving the OH ligands and 2-hydroxyquinoline or by iodido ligands, (2) mesomeric electron-withdrawing substituents on pyridine result in low-energy absorption with significant intensity in the visible region, and (3) the distinct makeup of the molecular orbitals in electronic transitions for cis/trans-{Pt(N3)2} isomers result in different photoproducts. In general, the comparison of the optimised geometries shows that Pt(IV) complexes with longer Pt−L bonds are more likely to undergo photoreduction with longer-wavelength light. Complex trans, trans, trans-[Pt(N3)2(OH)2(NH3)(4-nitropyridine)] was first synthesised. The experimental UV-Vis spectrum in aqueous solution correlates well with the intense band in the computed spectrum whereas the overlay in the low-energy absorption region can be improved by a solvent model. This combined computational and experimental study shows that TDDFT can be a design tool to tune the coordination environment for optimizing photoactive Pt(IV) compounds as anticancer agents without immediate need for synthesis. Additionally, molecular modeling is used to study DNA distortions induced by binding metal-containing fragments derived from cisdiamminodichloroplatinum( II) (cisplatin) and a new class of photoactive platinum anticancer drugs. Ligand field molecular mechanics (LFMM) parameters for Pt– guanine interactions are derived and validated against a range of experimental structures from the Cambridge Structural Database, published quantum mechanics/molecular mechanics (QM/MM) structures of model Pt-DNA systems and additional DFT studies. LFMM gives a good description of the local Ptguanine coordination at a fraction of the computational cost of QM/MM methods. The force field is then used to develop protocols for ligand field molecular dynamics (LFMD) simulations using experimentally characterised bifunctional DNA adducts involving both an intra- and an interstrand crosslink of cisplatin as a prelude to studying the interaction of trans-{Pt(py)2}2+ (P, py = pyridine), the major photoproduct of the novel platinum(IV) complex trans,trans,trans- [Pt(N3)2(OH)2(py)2] (17), with the DNA duplex dodecamer, d(C1C2T3C4T5C6G7T8C9T10C11C12)• d(G13G14A15G16A17C18G19A20G21A22G23G24). Based on the observed formation of a trans species when 17 is photoreduced in the presence of 5’-guanosine monophosphate plus the major-groove binding mode of the monofunctional complex cis-{Pt(NH3)2(py)}2+, P is proposed to coordinate to G7 and G19. This P-DNA adduct has a widened minor groove at one end of the platinated site and deepened minor groove at the opposite end, and exhibits a global bend of ~67° and an unwinding of ~20°. Brabec et al. subsequently demonstrated experimentally that such interstrand GG crosslinks can form as a result of the photoactivation of 17 in the presence of DNA. Such cross-links offer possibilities for specific protein–DNA interactions and suggest possible mechanisms to explain the high potency of this photoactivated complex

Amifostine reduces the seminiferous epithelium damage in doxorubicin-treated prepubertal rats without improving the fertility status

<p>Abstract</p> <p>Background</p> <p>Amifostine is an efficient cytoprotector against toxicity caused by some chemotherapeutic drugs. Doxorubicin, a potent anticancer anthracycline, is known to produce spermatogenic damage even in low doses. Although some studies have suggested that amifostine does not confer protection to doxorubicin-induced testicular damage, schedules and age of treatment have different approach depending on the protocol. Thus, we proposed to investigate the potential cytoprotective action of amifostine against the damage provoked by doxorubicin to prepubertal rat testes (30-day-old) by assessing some macro and microscopic morphometric parameters 15, 30 and 60 days after the treatment; for fertility evaluation, quantitative analyses of sperm parameters and reproductive competence in the adult phase were also carried out.</p> <p>Methods</p> <p>Thirty-day-old male rats were distributed into four groups: Doxorubicin (5 mg/kg), Amifostine (400 mg/kg), Amifostine/Doxorubicin (amifostine 15 minutes before doxorubicin) and Sham Control (0.9% saline solution). "Standard One Way Anova" parametric and "Anova on Ranks" non-parametric tests were applied according to the behavior of the obtained data; significant differences were considered when p < 0.05.</p> <p>Results</p> <p>The rats killed 30 and 60 days after doxorubicin treatment showed diminution of seminiferous epithelium height and reduction on the frequency of tubular sections containing at least one type of differentiated spermatogonia; reduction of sperm concentration and motility and an increase of sperm anomalous forms where observed in doxorubicin-treated animals. All these parameters were improved in the Amifostine/Doxorubicin group only when compared to Doxorubicin group. Such reduction, however, still remained below the values obtained from the Sham Control group. Nevertheless, the reproductive competence of doxorubicin-treated rats was not improved by amifostine pre-administration.</p> <p>Conclusions</p> <p>These results suggest that amifostine promotes a significant reduction of the doxorubicin long-term side effects on the seminiferous epithelium of prepubertal rats, which is reflected in the epidydimal fluid parameters in the adult phase. However, fertility status results suggest that such protection may not be effective against sperm DNA content damage. Further investigation of sperm DNA integrity must be carried out using amifostine and doxorubicin-treated experimental models.</p

Modelling and optimisation based drug delivery systems for the treatment of Acute Myeloid Leukemia (AML)

Leukemia is a malignant disease of the bone marrow and blood where immature white blood cells which are not able to develop into normal functioning blood cells are overproduced and build up in the bone marrow and blood. The most common treatment for most types of leukemia is intensive chemotherapy. This therapy can itself be life-threatening since only relatively few patient-specific and leukemia-specific factors are considered in current protocols; choice of chemotherapy, intensity and duration often depends on the treating physician’s experience with significant international protocol variability. With the advent of novel treatments and large amounts of patient- and leukemia-specific genomic data, there is a clear need for a systematic approach to the design and execution of chemotherapy regimens. We have developed a model for the simulation of patients with Acute Myeloid Leukemia (AML) undergoing treatment with two standard chemotherapy protocols, one intensive and the other non-intensive. The proposed model combines critical targets of drug actions on the cell cycle, together with pharmacokinetic (PK) and pharmacodynamic (PD) aspects providing a complete description of drug diffusion and action after administration. Tumour-specific and patient-specific characteristics are incorporated into the model in order to gain insights into the personalised cell dynamics during treatment. Sensitivity analysis of the developed model identifies cell cycle times as the critical parameters that control treatment outcome. For model analysis, clinical data of 6 patients who underwent chemotherapy are used for the estimation of cell cycle time distribution. The chemotherapy process is formulated as an optimisation scheduling algorithm aiming to obtain the chemotherapeutic schedule which would maximise leukemic cell kill (therapeutic efficacy) whilst minimising death of the normal cell population, thereby reducing toxicities. This optimisation algorithm is solved for all the patient case studies and the results clearly demonstrate the potential improvement of treatment design through optimisation.Open Acces

Development of novel anticancer agents targeting G protein coupled receptor: GPR120

The G-protein coupled receptor, GPR120, has ubiquitous expression and multifaceted roles in modulating metabolic and anti-inflammatory processes. GPR120 - also known as Free Fatty Acid Receptor 4 (FFAR4) is classified as a free fatty acid receptor of the Class A GPCR family. GPR120 has recently been implicated as a novel target for cancer management. GPR120 gene knockdown in breast cancer studies revealed a role of GPR120-induced chemoresistance in epirubicin and cisplatin-induced DNA damage in tumour cells. Higher expression and activation levels of GPR120 is also reported to promote tumour angiogenesis and cell migration in colorectal cancer. A number of agonists targeting GPR120 have been reported, such as TUG891 and Compound39, but to date development of small-molecule inhibitors of GPR120 is limited. This research applied a rational drug discovery approach to discover and design novel anticancer agents targeting the GPR120 receptor. A homology model of GPR120 (short isoform) was generated to identify potential anticancer compounds using a combined in silico docking-based virtual screening (DBVS), molecular dynamics (MD) assisted pharmacophore screenings, structure–activity relationships (SAR) and in vitro screening approach. A pharmacophore hypothesis was derived from analysis of 300 ns all-atomic MD simulations on apo, TUG891-bound and Compound39-bound GPR120 (short isoform) receptor models and was used to screen for ligands interacting with Trp277 and Asn313 of GPR120. Comparative analysis of 100 ns all-atomic MD simulations of 9 selected compounds predicted the effects of ligand binding on the stability of the “ionic lock” – a characteristic of Class A GPCRs activation and inactivation. The “ionic lock” between TM3(Arg136) and TM6(Asp) is known to prevent G-protein recruitment while GPCR agonist binding is coupled to outward movement of TM6 breaking the “ionic lock” which facilitates G-protein recruitment. The MD-assisted pharmacophore hypothesis predicted Cpd 9, (2-hydroxy-N-{4-[(6-hydroxy-2-methylpyrimidin-4-yl) amino] phenyl} benzamide) to act as a GPR120S antagonist which can be evaluated and characterised in future studies. Additionally, DBVS of a small molecule database (~350,000 synthetic chemical compounds) against the developed GPR120 (short isoform) model led to selection of the 13 hit molecules which were then tested in vitro to evaluate their cytotoxic, colony forming and cell migration activities against SW480 – human CRC cell line expressing GPR120. Two of the DBVS hit molecules showed significant (\u3e 90%) inhibitory effects on cell growth with micromolar affinities (at 100 μM) - AK-968/12713190 (dihydrospiro(benzo[h]quinazoline-5,1′-cyclopentane)-4(3H)-one) and AG-690/40104520 (fluoren-9-one). SAR analysis of these two test compounds led to the identification of more active compounds in cell-based cytotoxicity assays – AL-281/36997031 (IC50 = 5.89–6.715 μM), AL-281/36997034 (IC50 = 6.789 to 7.502 μM) and AP-845/40876799 (IC50 = 14.16-18.02 μM). In addition, AL-281/36997031 and AP-845/40876799 were found to be significantly target-specific during comparative cytotoxicity profiling in GPR120-silenced and GPR120-expressing SW480 cells. In wound healing assays, AL-281/36997031 was found to be the most active at 3 μM (IC25) and prevented cell migration. As well as in the assessment of the proliferation ability of a single cell to survive and form colonies through clonogenic assays, AL-281/36997031 was found to be the most potent of all three test compounds with the survival rate of ~ 30% at 3 μM. The inter-disciplinary approach applied in this work identified potential chemical scaffolds –spiral benzo-quinazoline and fluorenone, targeting GPR120 which can be further explored for designing anti-cancer drug development studies